It would be helpful to have diagrams for the OAuth flows. Here is an attempt ( code)
title OAuth User Agent Flow

participant "End User" as eu
participant "User Agent" as ca
participant "Apigee" as ap
participant "Login App" as lap

eu->ca: <>

ca->ap: /oauth/authorize (client_id,redirect_uri,scope)
ap-->ca: http_redirect (login_form,id)

ca-->eu: login_form [using native browser]
eu->lap: user login

lap-->eu: permission form [OAuth scopes]
eu->lap: user permission
lap->ap: GetAuthCode /oauth/authorizationcode\n (client_id,response_type,scope)
note over ap
Apigee will generate an access code\n or can be passed one. Authcodes \ncan have attributes like userid
end note
ap-->ca: http_redirect (auth_code)
ca->ap: GetAccessToken /oauth/accesstoken\n (auth_code,redirect_uri) \n+Header Authorization: Basic [base64 consumer key and secret]
note over ap
Apigee will generate token.\nAttributes set in authcode will \nbe copied over during token generation
end note
ap->ca: AccessToken

Provide your email address if you wish to be contacted offline about your comment.
We will not display your email address as part of your comment.

We'd love your feedback and perspective! Please be as specific as possible.
Type the characters you see in this picture. (verify using audio)

Type the characters you see in the picture above; if you can't read them, submit the form and a new image will be generated. Not case sensitive.